1887

Abstract

In considering the maintenance and repair of existing tunnels, it is necessary to determine the concrete lining thickness as well as the scope and depth of cavities behind concrete. Since ground penetrating radar (GPR) can rapidly provide high resolution continuous profiles and, is capable of detecting cavities and measuring concrete thickness, results in the frequent use of this method for these applications. Tunnel inspections however, present special problems due to traffic control and difficult access to the tunnel liner, especially in large diameter tunnels. Accurate assessments of cavity volumes is essential in estimating injection quantities during grouting operations. This requires complete coverage of radar profiles with accurate positioning information. As a result a special tunnel inspection vehicle, RAPIDAS, was developed for data acquisition. RAPIDAS is a vehicle mounted with four hydraulic booms. It can position up to four antennas simultaneously to the desired locations for radar measurements. It permits simultaneous and continuous profile measurements while the vehicle is moving. RAPIDAS is equipped with multiple channel radar systems to obtain high quality radar data in a short period of time. Special post processing software was also developed for quantitative analysis of the acquired radar data. For the calculation of cavity depths we have applied the least squares method between the basic wavelet and the observed wavelet in the frequency domain to obtain the reflection coefficient series. The effectiveness of the software was confirmed in model experiments and in field tests. For data processing we used both the newly developed software and RADAN (software ofthe GSSI Corporation). Post processing included background removal, amplitude adjustment and migration to emphasize the reflection wavelet from the reverse side oflining. Next, from features such as the magnitude of the amplitude and inversion of the phase, the scope of the cavity was extracted. Then a reflection coefficient series analysis was carried out with respect to the cavity location. The travel time in the cavity was obtained thereby confirming the cavity depth.

Loading

Article metrics loading...

/content/papers/10.3997/2214-4609-pdb.300.66
1994-06-12
2024-03-29
Loading full text...

Full text loading...

http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.300.66
Loading
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error